Normally the skins of the outer surfaces of the aircraft are manufactured by stretching. Forming machine parts must often meet aerodynamic requirements and visual aspects.
A major problem is spring back in parts such as leading edges and parts having double negative curvature (e.g., using bulldozer parts). See for example Maker et al, A Procedure for Springback Analysis Using LS-DYNA (Livermore Software Technology Corp. 2003), incorporated herein by reference.
To minimize residual stresses and deformations, prior techniques divided such parts into two pieces, which increased weight and cost and also affected visual appearance.
Spring back compensation has in the past been performed using a stretch machine, but many parts are now manufactured using a conventional fluid cell press that does not necessarily provide the same opportunities to assess spring back and perform spring back compensation as a stretch forming machine.
The use of springback compensation on curved surfaces (sheet metal) using the technique of finite element analysis minimizes the costs, the residual stresses and deformations in riveted structures of the aircraft.
The technology herein meets the visual appearance and aerodynamics of complex parts including those made of fabricated sheet metal.
It can be used to make narrow parts (e.g., leading edge and slats) and double negative curvature parts, and does not need to leave marks on the surface of the sheet so that visual aspects are not adversely affected.
The compensation technique, point to point uses approach equations with constant adjustability for curves. The constants (coefficients) used may depend on geometry and type of forming (stretch or hydraulic press). This example non-limiting process does not need to use mechanical properties of the material.
The technology herein can use compensated tooling of any type, irrespective of the method used for forming (stretching or pressing), processed at room temperature or heated for aluminum alloys.